Telephonic loud-speaker



April 15, 1930. F. w. LANCHESTER.

TELEPHONIG LOUD SPEAKER Filed May 25, 1929 IIIIIIIIIIIIIIYII EgZ.

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FREDERICK WILLIAM LANCEESTER, OF MOSELEY, BIRMINGHAM, ENGLAND TELEPHONIC LOUD-SPEAKER Application filed May 25, 1929. Serial No. 366,003, and in Great Britain April 14, 1928.

The present invention relates to an improved telephonic loud speaker and refers more particularly to an improved loud speaker of the moving coil type.

The present invention consists in a loud speaker comprising a sound producing mechanism an amplifying horn and an interconnecting conduit of constant bore and of length at least one quarter of the wave length 10 of the deepest tone which it is required to amplify.

The present invention further consists in a loud speaker comprising a sound producing mechanism an amplifying horn and an interconnecting tube of nonresonant material of constant bore and of length at least one quarter of the wave length of the deepest tone which it is required to amplify.

The present invention further consists in 2 a loud speaker comprising a sound producing mechanism, an amplifying horn and an interconnecting tube of lead of constant bore and of length at least one quarter of the wave length of the deepest tone which it is required to amplify.

In the accompanying diagrammatic draw- 1n s:

T igure 1 illustrates one convenient manner of carrying the present invention into effect.

Figure 2 illustrates a side view partly in section, of a modification.

Figure 3 is a front view thereof. According to the example illustrated in Figure 1 a field magnet is constructed in the manner commonly used in the cons-truction of moving coil instruments and the central core 0; thereof is drilled of suitable diameter, say from to i of the diameter of the annular pole gap. A diaphragm Z2 is made, preferably of mica, of conical form and to the periphery of this diaphragm a cylindrical former a is built on or cemented which carries the moving coil 65 adapted to be connected in series with the output circuit of an amplifier. The diaphragm is supported at its periphery by three or more cords or wires e which are preferably made adjustable in order to secure concentricity be- 59 tween the coil and the magnetic pole gap.

To the aperture or hole f of the central core a at the opposite end of the field magnet to the diaphragm is attached a tube or pipe 9 of substantially the same internal diameter as the bore aforesaid. This tube or pipe is preferably some three or four feet in length, or where the deepesttones of organ music are required to be reproduced it may be as much as eight or ten feet in length without disadvantage. It is also preferably non-res onant or substantially so. Thus heavy walled tube is desired and lead is preferred. To the distant end of this pipe is attached an expanding horn h of any well-known construction.

A convenient method of constructing and housing the whole combination is illustrated in Figures 2 and 8 in which the horn h is parallel sided in the vertical plane but eX- pands in horizontal plane. down of the horn passage is effected by the curved form of panels forming the base and roof of the horn. The progressive narrowing down, which may be based on a logarithmic law, is continued through the connection f pipe is at the end of which connection is made to the tube g, which conveniently con sists of a length of lead pipe housed within the space concealed by the curved top horn panel. The remote end of the said pipe g is carried through an aperture near the top of the piece of furniture and the electro-magneticdevice m is connected to the end of the pipe so as to be in an accessible position and so that its axis is horizontal.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is 1. A loud speaker comprising a sound producing mechanism, an amplifying horn and an interconnecting conduit of constant bore and of length at least one quarter of the Wave length of the deepest tone which it is required to amplify.

2. A loud speaker comprising a sound producing mechanism, an amplifying horn and an interconnecting tube of non-resonant material of constant bore and of length at least one quarter of the wave length of the deepest tone which it is required to amplify.

The narrowing 3. A loud speaker comprising a sound producing mechanism, an amplifying horn and an interconnecting tube of lead of constant bore and of length at least one quarter of the wave length of the deepest tone which it is required to amplify.

In testimony whereof I have signed my name to this specification.

FREDERICK WILLIAM LANCHESTER. 

